If you need to increase the maximum upload size for your WordPress Multisite (MU), you may do so by following the steps below:
Login to your WordPress Dashboard and click on My Sites >> Network Admin >> Settings.

Scroll down to the bottom to locate " Max Upload File Size " under Upload Settings section. The default value is 1500 KiloBytes which is 1.5 MegaByte. You may adjust this figure to a higher number according to your preference. In this example, I shall increase the number to 5 MB.

Once you're done, remember to press on the Save Changes button.
Login to your WordPress Dashboard and click on My Sites >> Network Admin >> Settings.

Scroll down to the bottom to locate " Max Upload File Size " under Upload Settings section. The default value is 1500 KiloBytes which is 1.5 MegaByte. You may adjust this figure to a higher number according to your preference. In this example, I shall increase the number to 5 MB.

Once you're done, remember to press on the Save Changes button.
Published on: 16 / 01 / 2019